Field of the Invention
The present invention relates to a controller for a mobile robot.
Description of the Related Art
In a mobile robot, such as a humanoid robot, which is composed of a base body and a plurality of links, which constitute leg link mechanisms or the like extended from the base body and which are interconnected through joints, the so-called position control is generally known (refer to, for example, Japanese Patent Application Laid-Open No. 5-305579). In the position control, the desired displacement amount of each joint is sequentially determined by inverse kinematics arithmetic processing or the like according to a desired motion (travel motion) of the mobile robot, and the displacement amount of each joint is controlled through a joint actuator such that the actual displacement amount follows the desired displacement amount.
According to the foregoing position control, the desired displacement amount of each joint is specified on the basis of a desired motion of the mobile robot, thus exhibiting poor flexibility in response to, for example, a change in an external force acting on the mobile robot.
In recent years, therefore, research has progressed on a technique for having a mobile robot travel by controlling the driving force for each joint through a joint actuator according to the so-called force control method.
According to the force control method, the desired driving force for each joint, i.e. each joint for moving a leg link mechanism, is determined by using an inverse kinematics model on the basis of a desired motion of the mobile robot, and the driving force for each joint is controlled through the joint actuator on the basis of the desired driving force.
In the case where the motion of a mobile robot is controlled according to the force control method, the displacement amount of each joint tends to change as an external force acting on the mobile robot (the contact reaction force from an external object) changes. This may cause the actual motion of the mobile robot to deviate from a desired motion or may impair the motion stability of the mobile robot.
Hence, it is considered desirable to estimate, by a certain means, the actual position and attitude (the position and attitude observed from outside the mobile robot) of a particular link, such as a link constituting the base body of the mobile robot, and to adjust, as necessary, the driving force for the joint supplied by the joint actuator on the basis of a difference between the estimated value and a desired value (the desired value in a desired motion) so as to reduce the difference.
In this case, desirably, the actual position and attitude of the particular link can be properly estimated by a simple method.